Overview
ISO 349:2020 - Hard coal - Audibert-Arnu dilatometer test specifies a laboratory method for determining the swelling (dilatation) properties of hard coal when heated under defined conditions in an Audibert‑Arnu dilatometer. The test records piston displacement of a pressed coal “pencil” inside a narrow calibrated tube as temperature increases, producing a dilatation curve that characterizes softening, contraction and maximum dilatation. The standard is intended for coking‑property assessment on a laboratory scale and is not designed to predict pressures in industrial coke ovens.
Key topics and technical requirements
- Scope and principle: Measurement of piston displacement vs temperature for a coal pencil in a dilatometer; key temperatures include softening (initial contraction), temperature of maximum contraction and temperature of maximum dilatation.
- Sample preparation and storage: Pulverized coal is formed into a standard pencil (e.g., nominal 60 mm length); susceptibility to oxidation is highlighted and reduced samples should be stored under oxygen‑free nitrogen to preserve properties.
- Apparatus:
- Mould, ram and press for preparing the coal pencil.
- Calibrated dilatometer tubes and steel pistons.
- Electric furnace designed for uniform heating (control up to 5 °C/min over typical ranges given in the standard).
- Thermocouple temperature‑measuring device (high precision).
- Cleaning tools for tube maintenance.
- Calibration and inspection: Procedures for calibrating temperature readings and for inspecting wear of tubes, pistons and moulds (including periodic comparisons after a set number of tests).
- Procedure and results: Defined heating rate, monitoring of piston displacement, expression of results as percentage changes of initial pencil length, and guidance on test reporting.
- Precision: Definitions and limits for repeatability (r) and reproducibility (R) are provided to support inter‑laboratory consistency.
Applications
- Laboratory evaluation of coking properties and swelling behavior of hard coal and coal blends.
- Quality control for coal suppliers and metallurgical coke producers.
- Research and development into coal thermal behavior, blend optimization, and laboratory‑scale screening of coals for coke production.
- Input data for coal selection and formulation in steelmaking and other industries relying on metallurgical coke.
Who should use this standard
- Coal testing laboratories and technical staff performing coal characterization.
- Coking plant R&D and quality assurance teams.
- Materials scientists and researchers studying coal thermomechanical behavior.
- Standards and conformity assessors involved in solid mineral fuels.
Related standards
- ISO 1213-2 - Vocabulary: terms relating to sampling, testing and analysis.
- ISO 13909-4 / ISO 18283 - Sampling and sample preparation guidance referenced for representativity and particle size.
Keywords: ISO 349:2020, Audibert‑Arnu dilatometer test, hard coal swelling, dilatometer, coking properties, laboratory test method.